1. Field of the Invention
The invention relates to a clutch unit comprising a contact plate, by means of which by axial displacement a clutch disk bearing friction linings forms a frictional contact and can be pressed onto a pressure plate, wherein the axial displacement of the contact plate can be caused by an axial displacement of a lever spring plate with a circular outer circumference, which bears against one or more bumps that are arranged in an annular manner on a surface of the contact plate facing towards the lever spring plate at a radial distance from the outer edge thereof, and wherein the contact plate has a ring-like, axially projecting edge radially outside on its side facing towards the lever spring plate.
2. Description of the Background Art
Clutch units are known from DE 10 2008 031 953 A1, which discloses a clutch unit, in particular a double-clutch unit for use in a double-clutch transmission. The known double clutch comprises two clutch disks, which can be connected to different input shafts of a downstream gearshift unit, wherein the transmission has two partial transmissions, between which gears can be shifted in a load interruption-free manner. The clutch disks bear friction linings, which can be clamped axially between a pressure plate common to the two clutches and respectively one contact plate assigned to the respective clutch. The pressure plate is supported by a bearing on the transmission side and fixed in the axial direction in order to axially absorb the closing forces necessary for the friction clutches. The contact plates are connected to the pressure plate in a torque-proof manner yet axially displaceable to a limited extent. A diaphragm spring-like lever spring plate having lever elements arranged in an annular manner is assigned to each contact plate. The lever spring plates have diaphragm spring-like properties, thus can be changed in their conicity in a resilient manner. At least one of the lever spring plates is arranged directly adjacent to the contact plate assigned thereto. In particular its lever elements bear against bumps on the surface of the contact plate facing towards it. These bumps are spaced radially apart from the edge of the contact plate and respectively act as a tipping point for the respectively bearing lever element. To actuate the clutch, the central region of the lever spring plate is displaced axially so that the lever elements exert an axially directed force on the contact plate in order to thus cause a corresponding axial displacement of the clutch disk, i.e., the clutch disk is pressed to the pressure plate. The contact plate has an annular, axially projecting edge radially outside on its on its side facing towards the lever spring plate, against which edge the radially outer ends of the lever elements bear and on which the leverage acts.
A disadvantage of the known clutch unit is its susceptibility to soiling. For instance, the contact plate with its axially projecting edge and the lever spring plate with its lever elements bearing against the axially projecting edge form a quasi-closed space in which dust penetrating from outside and wear debris collecting from inside, hereinafter referred to jointly as “sediment,” can be deposited. In the case of excessively thick sediment layers, obstruction of the mobility of the contact plate and thus difficulties in engaging gears can occur.